In the area of speech recognition, some voice controlled devices have a feature called “barge-in”. This feature allows the user to interrupt the speech dialog system during a speech prompt, or while some other audio signal is being transmitted. For example, for voice controlled navigation devices this may shorten the dialog considerably, as it is no longer needed to listen to the entire prompt, one which may already be known to the user. Further, in the case of a voice controlled television, the television may be playing the current television audio signal while the recognition engine has to decode the user's utterance at the same time. In this way, various signal processing techniques may be applied to the microphone signals in order to remove the prompt or television signal respectively. Thus, the system will no longer respond to this acoustic “echo”. This type of signal processing technique is referred to as Acoustic Echo Cancellation (AEC). Accordingly, in order to cancel out acoustic echoes in a microphone signal, the signal that is played back over the loudspeaker(s) has to be available for speech enhancement. If so, a filter may be applied to this reference signal such that an optimum estimate for the actual echo component at the microphone is obtained. This estimate may then be removed.